Chris Singh, owner of the Butterworth Party Store speaks about the armed robbery, which occurred at the 944 Butterworth St. SW location in Grand Rapids, Mich., Monday, April 28, 2014. (Andrew Kuhn | MLive.com)

GRAND RAPIDS, MI — A man in custody for allegedly robbing a Grand Rapids party store walked in the shop, jumped over a counter and began threatening two men with a handgun, video from store security cameras show.

The masked suspect is seen on surveillance video pushing a clerk and a friend to the ground at Butterworth Party Store while waving the firearm and pointing it at their heads.

The robber told one of the men to open the cash drawer, but then turned to the other man when he realized the first victim doesn't work there, one of the men behind the counter said after the robbery.

The suspect is shown standing over the clerk as he demands him to open the register and put money in a bag. The friend is forced to count to 20 with his head down.

The robber grabbed a handful of cigarette packs before he jumped back over the counter and ran across the street about 4:45 p.m. Monday, April 28.

It was a frightening and dangerous scenario that unfolded in about one minute, but Chris Singh, the owner of Butterworth Party Store, 944 Butterworth St. SW, said he's thankful one of the victims played a key role in police catching the suspect.

Pritpal Singh, who doesn't work at the party store and was there visiting, ran off after the suspect to see which direction he went. Passersby told Singh which way the robber fled, and he made the quick decision to hop in his car and follow the suspect's vehicle.

"It was just such a headrush," he said. "He didn't notice at that point that I'm following him."

Pritpal Singh said he was running on adrenaline.

"I was thinking all kinds of crazy stuff in my head," he said. "I could literally hear my heart beating in my ears."

On Fulton Street, the suspect noticed he was being tailed.

"I could literally see his eyeballs in his rear-view mirror that he was shocked like, 'OK, where's this guy coming from and why is he following me?'" Pritpal Singh said. "At that point, I was 100-percent sure this is the guy."

The suspect made a sharp turn down an alley and sped off. Pritpal Singh didn't follow because he didn't want to crash or risk hitting a pedestrian. He'd memorized the suspect's license plate by that point and relayed it to police back at the store.

Officers found the vehicle parked outside 835 Bridge St. NW, surrounded the home and took the suspect into custody. Grand Rapids Police Capt. Dan Savage said investigators will look into the possibility of others being involved and whether the robbery is connected to other recent heists in the city.